The wildlife of a small market town…

Month: September 2014

I wanted to share a rather unusual video clip which I captured on a trailcam recently. I know mink to be good swimmers but I did not realise they were tree climbers! Various sources suggest this is a known behaviour, with some suggesting they climb regularly whilst others suggest rarely. One website states that they frequently climb to escape predation although there is nothing to suggest that this was the case in this video.

One of the best applications of a camera trap is when it allows you to observe something unusual or unexpected which could not otherwise be obtained without hours of watching and waiting. I think this clip is a perfect example!

It is incredible what you find, when you start to look. There is a certain sloe which grows along the River Witham in Grantham, and for some reason it seems to beat every other blackthorn to bloom. I was walking along in March and saw a bumblebee visiting the flowers. It turned out to be a tree bumblebee – the first species I could name beyond ‘bumble’. Throughout the summer, I have added new bumblebees to my acquaintance as well as many other characters which together make up the family bee. I have very much more to learn and look forward to doing for many years to come, but I was amazed at just how much I have never noticed before. I have gone all these years and yet never seen mining bees visiting the garden, or the nomad bees lurking near their nests. I have never watched mason bees collecting mud or realised that they have their tunnels in the walls of our house. Tiny, beautiful solitary bees and huge queen bumblebees, leafcutters and honey bees and that’s before we even get on to all the pretenders; the hoverflies and beeflies which imitate and exploit! I have illustrated below just a few of those I have been lucky enough to see this year, I hope it might inspire you to explore for yourself.

Bumblebees

Early in the year, the queens emerge from hibernation and feast on the early flowering plants; the heathers and hellebores were a favourite in the garden whilst long-season gorse flowers are an ideal early-spring feed in the wild. These queens will establish nests and then the whole process of ID becomes more complicated as the workers and males appear – similar but subtly different to the queens of the species. There are 24 species in the UK but around six are the most commonly encountered; the Bumblebee Conservation website is a fantastic resource to get you started and with a few key ID tips, you are well on your way with most species!

These bees are so named because they dig holes in the ground in which to lay their eggs. There are around 100 species in the UK and they include some exquisitely beautiful specimens such as the tawny mining bee which is a stunning shade of autumnal red. The ashy mining bee and early mining bee also paid a visit to my garden this year. In contrast to the bumblebees, they are largely solitary although some species do nest communally.

These small bees are not immediately obvious to identify as such on first glance – they are rather more wasp-like than bee-like. There are around 30 different species and they parasitise the nests of other bees – especially mining bees – laying their eggs in the nests which gives rise to the alternative name of ‘cuckoo bee’. There are also cuckoo bumblebees which behave in a similar manner with the nests of bumblebees although I have not (yet) managed to spot one of these.

A nomad bee on gorse flowers at the Hills and Hollows in Grantham

Mason bees

There are several species of mason bees in the UK – these are so called because they use mud when constructing their nest. We have red mason bees nesting in holes in the pointing of our house but many different crevices and cavities can be used. The bees lay their eggs inside the tube structures and then seal the end with mud. I came across a ‘mud mine’ down beside the River Witham in Grantham where mason bees were coming and going collecting mud, with up to 10 present at any time. The hollows you can see in the photograph were excavated by these bees which gather up the mud and fly back to their nesting sites with it clutched between their mandibles.

A red mason bee (Osmia rufa) gathering mud from the bank of the River Witham in Grantham

Leafcutter Bees

These bees have a similar ecology to the mason bees, only they use leaves instead of mud as their medium of choice when sealing up their entrances. I spotted this one in our back garden but was lucky enough to watch one ferrying segments of rose leaf from a nearby bush to a bee-hotel in my parents garden. The semi-circular cuts around the edge of the leaf are quite distinctive when you’ve seen them once and a sure sign that these bees are around.

A leafcutter bee resting on a plantpot in my back garden

Solitary bees

There are a large number of small solitary bees which are often difficult to identify as they are so small and subtly different. This one was identified for me as a male Lasioglossum calceatum, probably the commonest of this particular genus in the UK.

There is only one honey bee species in the UK and it is quite distinct from the rest. Whilst the patterns may vary, the shape and general demeanor make them quite distinctive. Many honey bees belong to hives but wild populations also exist and you can see them from the first spring sunshine through to the last throes of summer.

Honey bee (Apis mellifera) leaving a Himalayan balsam flower

The active season for many invertebrates, including the bees, is coming to an end. Common carder bumblebees are still around in good numbers but it won’t be long until they too vanish from the flowers. I am already looking forward to next spring when the queens emerge from their hibernation and there will be a new host of commonplace marvels to notice for the first time. The sheer diversity is breathtaking – it only requires you to bend a little closer to the ground to take it in. I would cordially invite you to do so!

Common carder bumblebee (Bombus pascuorum) feeding at a fumitory flower

September marks the beginning of the end of the bats’ active season in the UK – the maternity roosts have disbanded, the juveniles are out fending for themselves, the bats are beginning to build up their reserves to hibernate through the winter, and bat workers begin to catch up on sleep for the first time since spring! What better time to hold the Annual Bat Conference, to share the new findings and discoveries of the summer!

The conference in Warwick this year opened with a talk from the BCT’s new joint CEO’s Julia Hamner and Kit Stoner outlining some of the great work that the conference organisers have been involved within in 2014. The voice of the bat community was one of the strongest in the government’s recent Wildlife Legislation consultation with over 50% of comments relating to bats. This gave the BCT a mandate to argue the case for the continuing the protection which our bats need to ensure their conservation status. Work is progressing on the newest revision of the Bat Workers Manual and a new area of the BCT website has been launched, dedicated to the provision of educational resources to help bat workers across the country to educate and enthuse others. Permitted development is a current concern with anecdotal evidence suggesting that bats are being missed out of the process and thus roosts are being damaged or destroyed in contravention of the legislation. BCT are calling for case studies and reports from anybody who can provide evidence or information on the validity of these concerns.

Landscape use by bats seemed to link a number of talks, with several researchers sharing the insights they have gained through radiotracking studies. This theme was kicked off with Katherine Boughey of BCT talking about the power of Geographic Information Systems (GIS) for collating over 10 years of volunteer data gathererd through the National Bat Monitoring Programme (NBMP). This can be manipulated and analysed to discover trends in the distribution of roosts and species. The BCT have produced a map of bat diversity throughout the country, showing the highest species diversity in the south west with a steady decrease as you move north and east. The data is made available to local Bat Groups in Google Earth layers and they have worked with individual Bat Groups to develop an atlas of their county, combining the NBMP data with records which the bat groups hold themselves. Katherine also outlined concerns with the current way in which data searches for protected species are conducted and explained the Core Sustenance Zone principle. Under this model, the criteria for a data record (such as a bat roost) appearing in a search would not be simply dictated by an arbitrary distance from a development but would be related to the ecology and behaviour of the species in question. The example used was to compare a great crested newt pond at 500m with a soprano pipistrelle roost at 2km – a development is much more likely to affect the more distant pipistrelle roost than the GCN pond as newts rarely travel this far from their breeding ponds. However a 1km search would exclude this roost.

A soprano pipistrelle bat in a gloved hand

The distance travelled by pipistrelle bats was elaborated on further by Madeleine Ryan from the University of Bristol. Her research involved radio tracking bats from core maternity roosts in churches, and finding their alternative roosts as well as their foraging areas and home ranges. Madeline found a variety of home range sizes for different colonies in different parts of the country, with a colony in Essex regularly flying 10km to reach a particularly large and insect-abundant reservoir after darkness fell whilst bats from other colonies travelled only 2-3km per night. Although the colonies in Cambridgeshire and Norfolk commuted shorter distances, each colony had a similar resource – such as a reservoir or other large waterbody – which seemed to be of key importance with most or all of the bats foraging there, after first starting the night feeding in darker woodlands and riparian habitat close to their roost sites.

Maggie Brown of the West Yorkshire Bat Group described their radiotracking study on noctules which were taken into care over the winter and then released with tags in the spring. The female disappeared almost immediately and was never detected again, potentially suggesting that she flew far away from the location where she was found. The second bat, a male, spent much of his time on a scarp above the river in the town, often spending time foraging over the town centre and at one point appearing to roost in a town-centre building. This gives some confidence that bats released from care do survive well and return to their natural habits, although caution must be exercised in drawing conclusions from a single bat.

Madeline Ryan’s talk also looked at the importance of church roosts to soprano pipistrelles. These bats often aggregate into large maternity colonies and can cause conflict with the wardens and worshipers of the churches they inhabit. An oft-heard argument for exclusion is that the bats can simply roost elsewhere. Whilst Madeline’s study found a number of other roosts, many of these were small roosts used by individual bats and only 10% were communal roosts of the type which are so important to successful rearing of offspring.

Matt Zeale presented the findings of studies where the behaviour of soprano pipistrelle colonies were monitored before and after exclusion from a house where the home owners had identified an issue. He found there was little change in the foraging behaviour of the bats and that new colonies often established within 3 days of the exclusion. A large number of the alternative roosts were used both before and after exclusion and the study concluded that the colonies appeared able to deal well with the exclusion. However, in many instances, the colonies re-grouped in a nearby house or building of similar construction, where they found similar conditions. This, it could be argued, is simply moving the bats from one location to another where the same issues may arise and the same action required once again – hardly a satisfactory solution.

A more positive approach was described in a talk by John Haddow about the works undertaken to limit the impacts of a large soprano pipistrelle roost on the occupants of a residential house in Scotland. The roof was cleaned and restored and a box was built to contain the bats within a particular area of the roof where there would be less impact of noise or guano. This was of limited success with the colony instead moving to another part of the building, but mitigation features such as this often take time to work and it is hoped that the bats may utilise this alternative roost in the future. In the mean time, the actions taken by the Bat Group did have the effect of reducing many of the other effects of the bats occupancy which could represent an issue to the homeowners.

Steve Roe of the Derbyshire Bat Group gave a summary of mitigation works undertaken at the Elvaston Boathouse. Works were needed to restore the boathouse which played host to a large colony of Daubenton’s bats – a species which is most commonly found foraging over waterbodies. The colony were roosting in a narrow crevice formed between two timber lintels, and an exact replacement of this feature in the new building ensured that the colony continues to use the feature 20 years on. Steve showed some excellent footage of the bats stretching before leaving their roost which you can view here.

Provision of artificial structures was one of the elements of Jane Sedgeley-Strachen’s talk on the Vincent Wildlife Trust’s Beacon for Bats project aimed at lesser horseshoe bats in mid-Wales. The project was wide ranging with much work done on the identification of the bats roosts, foraging habitat and commuting routes. This led to enhancement measures such as the improvement of roosts and foraging habitat, planting to increase landscape level connectivity and a wide range of community involvement elements to engage and enthuse a team of local volunteers. One proposals which proved more difficult than anticipated was the erection of night roosts within woodlands – this surprisingly required planning permission bur fortunately the addition of wheels seemed to provide the loophole required to install these features in the National Park woodlands. Night roosts are locations where horseshoe bats, as well as other species such as brown long-eared bats, hang up during the night to eat their prey before taking to the wing to catch more. These ‘dog kennels’ were quickly utilised by the resident bat populations and their designs have been published by the Vincent Wildlife Trust.

Two very informative talks were given on quite a contentious topic – bats and wind turbines. Oliver Behr’s talk on the Saturday was the first of these – he described research done to model the mortality risk for bats based on acoustic surveys and the weather conditions. Higher risk conditions were identified, relating to the presence of bats as well as the wind speed, the time of night and the time of year. This led to the development of bat-friendly algorithms which run the turbines, turning them off at the high risk times. This led to a six-fold reduction in the number of bats killed – a significant improvement considering the loss of revenue from electricity generated under these bat-friendly algorithms is only around 1%. Many of the commercial wind turbines across Germany are now running on these systems.

Fiona Matthews gave a summary of her research into the impacts of wind turbines on bats in the UK. This study is still unpublished but it is hoped that it will be available soon. Fiona surveyed 23% of large scale UK wind turbines using a range of techniques including acoustic surveys at height and on the ground, transect surveys and mortality searches using trained sniffer dogs to identify bat corpses below the rotor sweep of the turbines. Some of her findings appear to cast doubt on the current methods of assessment for wind turbine development; she found large variation in activity levels between different nights – indicating that a large temporal scale over at least 3 weeks may be required to fully appreciate the risk factor – and that there was little correlation between noctule and pipistrelle activity levels at height and on the ground – highlighting the need for activity surveys at the nacelle height. Fiona also highlighted concerns with our ability to assess the potential impacts of individual mortality on a population scale, considering the poor state of knowledge on bat populations and distributions in the UK, coupled with the difficulty in assessing mortality rates under suboptimal conditions where crops may prevent access or scavengers may beat you to find the corpses. This talk was interesting, concerning and incomplete as the research can not yet be published – it is critical that the findings of this studies is made available as soon as possible so that the results can inform effective design, placement and assessment of turbine projects in the future.

The Wildlife and Artificial Light symposium earlier this year highlighted the potential impacts of artificial lighting on a range of nocturnal species, with a particular emphasis on bats. Danilo Russo described an increase in cranial size of Kuhl’s pipistrelle in Italy, which corresponded perfectly with the massive increase in artificial lighting of public spaces which occurred in the 1950’s. Danilo’s hypothesis for this increase was the effect of light on tympanal moths. These moths have an ‘ear’ which allows them to hear bat echolocation and take evasive action to avoid being caught. It has been shown that light reduces this avoidance response in moths which makes them much more susceptible to bats. The pipistrelle bats therefore began to exploit this newly available resource and the larger size of the moths over their regular prey meant that a larger jaw and stronger bite gave bats with a larger cranial size a competitive advantage.

Two talks focused on the bat fauna of countries beyond our shores here in the UK. Rachael Cooper-Bohannon described work assessing the distribution of bats in southern Africa as part of the Bats without Borders project. There are more than 120 different species but little research has been done on their ecology and distribution. The team projected the distribution of species based on their known locations – called Species Distribution Modelling – and identified the hotspots of biodiversity, as well as areas where particular families had a stronghold. The highest diversity overall was in the dry and wet savannah and afro-montane areas, whilst most species avoided the arid areas. The Rhinolophid species – the family to which our UK horseshoe bats belong – was the exception to this trend, being frequently encountered in dryer regions.

Ludmilla Aguiar dubbed Brazil the ‘Land of Bats’ – they have 15% of the world’s bat totaling over 179 species. The slideshow had many fascinating looking bat species which belong to a wide range of families with different ecologies, including insectivorous and frugivorous species as well as the infamous vampire bats. Ludmilla described some of the research being undertaken on these bats, and the threats which they are under through negative press such as the association of vampire bats with rabies. We have some fairly uninspired names for our UK species – the brown long-eared being a case in point – but my favourite Brazilian bat mentioned in the talk was Lasiurus ebenus, commonly known as the ‘blackish red bat’.

The search for new records of the most recently confirmed British species – the Alcathoe bat – was described by Philip Brown who undertook research into this subject in 2013. The Alcathoe bat is morphologically and acoustically very similar to two other small myotis bats, the whiskered and Brandt’s bats, which is the reason that it remained unknown until very recently. The initial records were from Sussex and Yorkshire with no known presence in between. Throughout the summer of 2013, a large number of bats were caught by Philip and his helpers, and more records were gathered from other bat workers throughout the UK who had captured bats whiskered/Brandt’s/Alcathoe (WAB) bats in the course of their own research. A total of 110 WAB bats were identified using DNA analysis of which 95 were whiskered, 5 were Alcathoe and 10 were Brandt’s. Sadly the Alcathoe records did not extend the currently known range of the species, although Derbyshire Bat Group announced at the conference that a recent swarming survey they had undertaken in 2014 had led to the discovery of an Alcathoe bat in Leicestershire.

The photograph of the new Alcathoe bat record identified in Leicestershire by Steve Roe of the Derbyshire Bat Group

The potential for a new monitoring scheme was the subject of a talk by John Altringham who has developed a protocol for surveying woodland bat species. The hope is that this methodology, which uses Petterson detectors and a piece of software developed by the team, can be used by volunteers up and down the country to identify the occupancy of woodland bats including rarer species such as Bechstein’s and barbastelle. Sixty woodlands would need to be surveyed three times throughout the year to allow the populations of these species to be monitored. It is hoped that the scheme could be rolled out as part of the BCT’s National Bat Monitoring Programme (NBMP) in the future.

The provision for bats within the New Land Management Scheme (NLMS) was described by James Phillips of Natural England – this is the new agri-environment scheme which will be launched in 2015. The scheme will have a ‘two tier’ approach to delivery conservation benefits for species. All UK bat species will be included within the Mosaic approach which aims to provide broad, habitat scale enhancements which would benefit a wide range of species. Some specific species which are of higher conservation concern would also be catered for through the Bespoke approach – this would involve much more targeted actions and a higher level of advice and input from Natural England on the way in which the land is managed. Species falling within this Bespoke approach would include greater horseshoe, lesser horseshoe, grey long-eared and Bechstein’s bats.

Morgan Bowers gave a very illustrative talk on the new flight cage built by the Birmingham Bat Group – Brum Bats. The drive behind this was to have somewhere to exercise and assess captive bats to establish whether they were ready to be released and to allow them to learn flight skills in a safe environment. The end result is an excellent facility which has already had over 100 bats through its doors and is proving to be a valuable resource for trainee bat carers as they can learn to handle bats in a safe environment. You can watch footage of pipistrelle bats using the flight cage on Brumbats’ Youtube channel.

My personal highlight of the conference was the workshop talk given by Laura Grant on migration in UK bats. Many European species migrate, including species which are found in the UK such as noctule and Nathusius pipistrelle. Around 3% of bat species globally are known to migrate and this has developed in separate genetic lineages to allow the bats to make annual movements to where conditions or resources are optimal – for example to hibernate in suitable conditions or to exploit a seasonal abundance in food supply. Laura described a suite of studies and methodologies used to assess the migration of Nathusius pipistrelles between the UK and Europe – these included banding surveys where individual bats are ringed, stable isotope analysis to work out the broad geographic region where a bat was resident at its previous moult, and acoustic surveys such as those undertaken by BSG which looked at the comparative frequencies of different bat species at the predicted key migration points. These latter studies found that Nathusius pipistrelle had a different pattern of peak activity to other UK species recorded at the locations, with a focus around spring and especially autumn when it is predicted that the species would arrive at or leave our shores. More on Nathusius pipistrelles can be found here and a video of the Nathusius pipistrelle project in London is available here.

Once again, the BCT succeeded in putting on an inspiring and educational programme with talks ranging from mitigating individual roosts to broad scale impacts to populations, education on the bat fauna of other countries and current research which tells us more about the behaviour of our familiar UK species. The only downside with the conference is that it peaks your enthusiasm just as the bats’ active season is drawing to a close, but the bat groups rarely let this slow them down and they undertake hibernation checks at a range of roosting sites throughout the winter months – find your local group and get involved with these fascinating creatures. For more information on next year’s conference and on other events run by the BTC, check out their events page.